LXR linux/samples/bpf/tcp_cong

   1/* Copyright (c) 2017 Facebook
   2 *
   3 * This program is free software; you can redistribute it and/or
   4 * modify it under the terms of version 2 of the GNU General Public
   5 * License as published by the Free Software Foundation.
   6 *
   7 * BPF program to set congestion control to dctcp when both hosts are
   8 * in the same datacenter (as deteremined by IPv6 prefix).
   9 *
  10 * Use "bpftool cgroup attach $cg sock_ops $prog" to load this BPF program.
  11 */
  12
  13#include <uapi/linux/bpf.h>
  14#include <uapi/linux/tcp.h>
  15#include <uapi/linux/if_ether.h>
  16#include <uapi/linux/if_packet.h>
  17#include <uapi/linux/ip.h>
  18#include <linux/socket.h>
  19#include <bpf/bpf_helpers.h>
  20#include <bpf/bpf_endian.h>
  21
  22#define DEBUG 1
  23
  24SEC("sockops")
  25int bpf_cong(struct bpf_sock_ops *skops)
  26{
  27        char cong[] = "dctcp";
  28        int rv = 0;
  29        int op;
  30
  31        /* For testing purposes, only execute rest of BPF program
  32         * if neither port numberis 55601
  33         */
  34        if (bpf_ntohl(skops->remote_port) != 55601 &&
  35            skops->local_port != 55601) {
  36                skops->reply = -1;
  37                return 1;
  38        }
  39
  40        op = (int) skops->op;
  41
  42#ifdef DEBUG
  43        bpf_printk("BPF command: %d\n", op);
  44#endif
  45
  46        /* Check if both hosts are in the same datacenter. For this
  47         * example they are if the 1st 5.5 bytes in the IPv6 address
  48         * are the same.
  49         */
  50        if (skops->family == AF_INET6 &&
  51            skops->local_ip6[0] == skops->remote_ip6[0] &&
  52            (bpf_ntohl(skops->local_ip6[1]) & 0xfff00000) ==
  53            (bpf_ntohl(skops->remote_ip6[1]) & 0xfff00000)) {
  54                switch (op) {
  55                case BPF_SOCK_OPS_NEEDS_ECN:
  56                        rv = 1;
  57                        break;
  58                case BPF_SOCK_OPS_ACTIVE_ESTABLISHED_CB:
  59                        rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
  60                                            cong, sizeof(cong));
  61                        break;
  62                case BPF_SOCK_OPS_PASSIVE_ESTABLISHED_CB:
  63                        rv = bpf_setsockopt(skops, SOL_TCP, TCP_CONGESTION,
  64                                            cong, sizeof(cong));
  65                        break;
  66                default:
  67                        rv = -1;
  68                }
  69        } else {
  70                rv = -1;
  71        }
  72#ifdef DEBUG
  73        bpf_printk("Returning %d\n", rv);
  74#endif
  75        skops->reply = rv;
  76        return 1;
  77}
  78char _license[] SEC("license") = "GPL";
  79